Marksmanship training device

ABSTRACT

The present invention describes a marksmanship training simulator including, a weapon capable of firing a laser, a screen for projecting images including a background and a target thereon using a background projector for projecting a background scene and a target area projector for projecting a density of visible pixels on the screen such that the target image is at better than eye-limited resolution when viewed by the marksman through a and wherein the contrast ratio of the target image formed by both by the background and target area projector is substantially that of the target area projector. The screen reflects the laser and there is also a laser footprint detector directed to the target area wherein the density of the detector pixels for receiving the non-visible footprint and the intensity and size of the laser footprint is such that there is a predetermined accuracy of the detection of the location of the footprint.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/414,559, filed May 1, 2006, entitled “Marksmanship TrainingDevice.”

FIELD OF THE INVENTION

The current invention relates to a simulator for training small armsmarksmanship skills which involve firing over long distances and wherethe required angular movement of the barrel is slow.

BACKGROUND OF THE INVENTION

There are numerous weapon simulator devices that have been utilized fortraining marksmen and other personnel for combat situations, as well asfor law-enforcement. The technology enabling the construction of suchdevices started becoming viable with the introduction of solid-stateelectronics in the 1970's. Over the last two decades the scientificcommunity has conducted controlled experiments in order to evaluate theeffectiveness of these devices for training and assessing marksmen. Noneof the experiments have found evidence of any significant benefit formarksmanship training, in particular the ability to locate a group ofshots in tight proximity onto a target. Furthermore, none of the studieshave found high correlations between marksmanship performance in thesimulator and that in the live environment (i.e., a marksman's live-fireperformance is not well-predicted by their performance in thesimulator). Such outcomes imply that these devices have limited utilityfor training and assessing marksmanship skills. While the scientificliterature has highlighted these shortcomings, the scientific communityhas tended to caution against over reliance on the use of thesesimulators and have not identified any solutions to these problems interms of improvements to the simulator.

The task of marksmanship requires the use of very fine perceptual-motorskills. In general, marksmanship tasks can be divided into two types.The first type involves firing over long distances at targets subtendingsmall angles at the weapon (e.g., a marksman firing at a static targeton a rifle range at 100 metres, or a sniper attempting to fire at apartially concealed man-size target at several hundred metres). Thistype of task is best conducted from the prone position mainly becausethis enables the shooter to steady the barrel, and because engagement ofthe static or slow-moving target does not require rapid angular movementof the barrel of the weapon. The second type of marksmanship taskinvolves firing at close-range, fast-moving targets, such as occurs incombat pistol tasks and in the recreational field of clay-pigeon orskeet shooting. This latter task is typically conducted from a standingposition to give the marksman greater freedom of movement and allowrapid angular movement of the barrel of the weapon. However, thesefactors lead to less stability of the barrel, which in turn leads toless accuracy in aiming the weapon and hence this type of task is moreoften conducted over closer ranges.

Computer generated target imagery found in current small arms simulatorsis limited by the resolution of that imagery which is significantlylower than the eye-limited resolution of targets on a live firing rangeand thus the degraded target results in significant shortcomings inmarksmanship performance. When training marksman to aim, acquire andengage a target, it is important that the limiting factor is the visualacuity of the marksman and not visual artifacts in the simulated targetimage.

Marksmanship performance is often measured in terms of a hit or miss ofthe target. It is acknowledged that hitting a target is an importantmeasure of performance in marksmanship training. However, whenundertaking marksmanship training, other important measures include theextreme spread which is the distance between the two most widelyseparated shots in a group of shots and shows the ability of themarksman to maintain a consistent point of aim. When specifying theaccuracy requirements for the weapon aim-point calculation in amarksmanship simulator, it should be apparent that any measurement errorshould be insignificant compared to the requirements of the marksmanshiptask being trained or assessed. In current small arms simulators, theweapon aim-point and fall of shot position locations are not calculatedby the hit detection systems to a level of precision sufficient tosupport the reliable assessment and training of marksmanship skills, inparticular for shooting at targets over long ranges.

The invention described herein provides a method and apparatusarrangement to overcome, or at least substantially reduce thedisadvantages and shortcomings in prior art by ensuring that themarksman's performance is not confounded by (a) the quality of thetarget image and/or (b) the accuracy of the weapon aim-pointdetermination.

Thus a simulator arrangement and method of use is described for trainingmarksmanship tasks which involve firing over long distances and wherethe required angular movement of the barrel is slow.

Additionally further advantages of the present invention will becomeapparent from the following description, in connection with theaccompanying drawings, where, by way of illustration and example,embodiments of the present invention are disclosed.

BRIEF DESCRIPTION OF THE INVENTION

In a broad aspect of the invention a marksmanship simulator for thetraining of a marksman includes: a target area projector projecting adensity of pixels on the screen than such that an individual pixel isnot visible to the vision assisted or vision non-assisted marksman,wherein the pixels form a target image within the target area; a screenfor receiving and reflecting projected visible and non-visibleradiation; a background projector for projecting an image on the screenand over a target area, wherein the contrast ratio of the target imageformed by both the background projector and target area projector issubstantially that of the target area projector.

In a further aspect of the invention a marksmanship simulator furtherincludes a marksmanship training weapon for projecting a non-visiblelaser footprint onto the screen; and a detector for detecting thereflected non-visible laser footprint on the screen wherein the densityof the detector pixels for receiving the non-visible footprint and theintensity and size of the laser footprint is such that there is apredetermined accuracy of the detection of the location of footprint.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a processor for receiving the detector signalrepresenting the location of the non-visible laser footprint and alsoknowing the location of the projected pixels of the background image andtarget area and determining the location of the non-visible laserfootprint with respect to one or more of the pixels of either or boththe background image or the target area.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a detector arranged to detect the non-visible laseronly if it lies near or within the target area.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a background projector which maximizes the contrastratio in the target area by minimizing the brightness in the target areaprojected by the background projector.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a mechanism for moving both the target area projectorand the detector such that the detector is detecting the non-visiblefootprint in or about the target area.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a marksmanship arrangement having a screen forreceiving and reflecting projected visible and non-visible radiation, aprojector for projecting a density of visible pixels on the screensubstantially within a target area and a marksmanship training weaponfor projecting a non-visible laser footprint onto the screen, includinga detector for detecting the reflected non-visible laser footprint onthe screen wherein the density of the detector pixels for receiving thenon-visible footprint and the intensity and size of the laser footprintis such that there is a predetermined accuracy of the detection of thelocation of footprint.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a marksmanship training weapon for projecting anon-visible radiation footprint including a target area image capable orreflecting non-visible radiation, and a detector for detecting thereflected non-visible radiation footprint from the target wherein thedensity of the detector pixels for receiving the non-visible footprintand the intensity and size of the laser footprint is such that there isa predetermined accuracy of the detection of the location of footprint.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a marksmanship simulator wherein the target area imageis illuminated.

In yet a further aspect of the invention a marksmanship simulatorfurther includes a marksmanship simulator wherein the target area imageis illuminated by non-visible light.

It should be appreciated that the present invention can be implementedin numerous ways, including as a process, an apparatus, a system, or acomputer readable medium such as a computer readable storage medium or acomputer network wherein program instructions are sent over wireless,optical or electronic communication links. It should be noted that theorder of the steps of disclosed processes may be altered within thescope of the invention.

Details concerning computers, computer networking, software programming,telecommunications and the like may at times not be specificallyillustrated as such were not considered necessary to obtain a completeunderstanding nor to limit a person skilled in the art in performing theinvention, are considered present nevertheless as such are considered tobe within the skills of persons of ordinary skill in the art.

A detailed description of one or more preferred embodiments of theinvention is provided below along with accompanying figures thatillustrate by way of example the principles of the invention. While theinvention is described in connection with such embodiments, it should beunderstood that the invention is not limited to any embodiment. On thecontrary, the scope of the invention is limited only by the appendedclaims and the invention encompasses numerous alternatives,modifications, and equivalents. For the purpose of example, numerousspecific details are set forth in the following description in order toprovide a thorough understanding of the present invention. The presentinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the present invention is notunnecessarily obscured.

Throughout this specification and the claims that follow unless thecontext requires otherwise, the words ‘comprise’ and ‘include’ andvariations such as ‘comprising’ and ‘including’ will be understood toimply the inclusion of a stated integer or group of integers but not theexclusion of any other integer or group of integers.

The reference to any background or prior art in this specification isnot, and should not be taken as, an acknowledgment or any form ofsuggestion that such background or prior art forms part of the commongeneral knowledge.

Specific embodiments of the invention will now be described in somefurther detail with reference to and as illustrated in the accompanyingfigures. These embodiments are illustrative, and not meant to berestrictive of the scope of the invention. Suggestions and descriptionsof other embodiments may be included within the scope of the inventionbut they may not be illustrated in the accompanying figures oralternatively features of the invention may be shown in the figures butnot described in the specification.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a marksmanship simulator arrangement of an embodiment ofthe invention;

FIG. 2 depicts alternative arrangements according to embodiments of theinvention for projecting the target image onto a screen;

FIG. 3 depicts prior art projection of the background and target imageusing a background projector;

FIG. 4 a depicts prior art target area resolution and target image asdisplayed by the background projector and as seen by a marksman;

FIG. 4 b depicts target area resolution and target image as displayed bythe target projector wherein the target image is at better thaneye-limited resolution as seen by the marksman according to anembodiment of the invention;

FIG. 5 illustrates the geometry associated with the calculation of themaximum projected pixel size to achieve an eye limited resolution of thetarget area;

FIGS. 6 a and 6 b show light intensity plots on the simulator screen forpurposes of illustrating the effect of two projectors on the contrastratio of the background and target area images;

FIG. 7 depicts prior art detection of the laser footprint.

FIGS. 8 a, 8 b and 8 c depict the characteristics of the laser footprintwhere the size of the laser footprint is larger than that of eachdetector pixel, and the pixel intensity before and after application ofa suitable threshold;

FIGS. 9 a, 9 b and 9 c depict the characteristics of the laser footprintwhere the size of the laser footprint is smaller than that of eachdetector pixel, and the pixel intensity before and after application ofa suitable threshold;

FIG. 10 depicts detection of the laser footprint for an embodiment ofthe invention.

FIGS. 11 a and b depict the characteristics of the laser footprint forone embodiment of the invention where the size of the laser footprint islarger than that of each detector pixel, and the pixel intensity beforeand after application of a suitable threshold;

FIGS. 12 a and b depict the characteristics of the laser footprint forone embodiment of the invention where the size of the laser footprint issmaller than that of each detector pixel, and the pixel intensity beforeand after application of a suitable threshold;

FIG. 13 depicts a flow diagram of the hit detection process;

FIG. 14 illustrates the pixel intensity before the application of asuitable threshold as described in FIG. 13;

FIG. 15 illustrates the pixel intensity after the application of asuitable threshold as described in FIG. 13;

FIG. 16 depicts a geometric representation of steps 8-13 in the hitdetection process for FIG. 13;

FIG. 17 depicts the output provided by the processor as feedback tomarksman and instructors.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

As mentioned previously, the target image is preferably presented to themarksman at better than eye-limited resolution. In the context of amarksmanship simulator, the term “eye-limited resolution” is taken tomean a simulated target image of such quality that when a marksman, withnormal (that is 20/20 vision), looks through the simulator aiming devicesees a target that does not have any additional visible artifacts thatare not present in the equivalent real-world target. In particular, withregards to this invention, such an image is provided under thoseconditions when the marksman can not detect individual picture elements(in a digital display the term pixel is used to describe such anelement). The image seen by the marksman is thus absent of anyindication that it has been generated electronically even though it willbe understood by the marksman that the image has been projected from anelectronic image generating device.

Referring to FIG. 1 an embodiment of one aspect of the invention isdepicted, including a marksmanship training weapon 1 for projecting anon-visible laser footprint onto the screen 6. The weapon is shown withan eye-sight aim assistance device, typically referred to as a sight 2,for viewing the target image 19. The target area 8 contains an image 19which can be viewed through the sight 2 of the weapon 1 to give a fieldof view 10. The weapon 1 includes a laser that emits radiation in theform of a non-visible laser beam (although other forms of radiation maybe useable) from the barrel 3 of the weapon which strikes the screen 6which receives and reflects the projected non-visible laser footprint,the footprint 7 being preferably, according to the skill of themarksman, within the target area 8.

A target area 8 can be projected anywhere on the screen 6 by the targetarea projector 16, this may be a bulls-eye or other type of target usedfor marksmanship training (animate or inanimate object) along with asuitable background image 9 (none specifically shown).

A background projector 4 projects an image 9 on the screen 6 andinvariably also over the target area 8, in this embodiment thebackground projector is Sony CX70 Ultra Portable LCD Data Projector, AVCentral, Adelaide, South Australia; a target area projector (Sony CX70Ultra Portable LCD Data Projector, AV Central, Adelaide, SouthAustralia), (target area projector 16) projects on to the screensubstantially within the target area 8, a density of visible pixels onthe screen such that the target image is at better than eye-limitedresolution when viewed by the marksman through the sight 2, and as willbe described in greater detail later in the specification, wherein thecontrast ratio of the target area formed by both by the backgroundprojector 4 and target area projector 16 is substantially that of thetarget area projector 16 so as to provide the best possible target imageto the marksman.

Continuing reference to FIG. 1, in this embodiment, a non-visibleradiation detector (in this embodiment a laser footprint detector) 18 isdirected to detect the target area 8 on the screen 6. The detector (inthis embodiment a Photron PCI 512 Fastcam, Blink Technology Australia,Pty Ltd) for detecting the reflected non-visible laser footprint on thescreen is arranged such that the density of the detector pixels forreceiving the non-visible footprint and the intensity and size of thelaser footprint is such that there is a predetermined accuracy of thedetection of the location of the footprint as described in greaterdetail later in the specification. To determine the parameters of thedensity of the detector pixels and the intensity and size of the laserfootprint requires consideration of the measurement accuracy requiredfor the marksmanship task being trained or assessed. For example, apass/fail criterion may be the requirement to achieve an extreme spreadless than 200 mm when shooting at a target at 100 m on the live range.This would then lead to the requirement to discriminate between extremespreads over a range encompassing values below and above this pass/failcriterion. This leads to a requirement to be able to discriminate towell below the pass/fail criterion. In this example this could beapproximately 25% of the pass/fail criterion (that is 50 mm). Themeasurement accuracy required to achieve this level of discriminationconsequently may be an order of magnitude better than the 50 mm taskrequirement; that is the detection system would be required to have ameasurement accuracy of equivalent to 5 mm on a real target. In amarksmanship simulator, where the marksman may fire at a distance of 10m from the screen, by geometry (similar triangles), the measurementaccuracy requirement in the simulator would therefore be 0.5 mm.

The detection process in one embodiment uses a processor 11 which isconnected to both the background projector 4, the target area projector16, and in particular the laser footprint detector 18 so as to determinethe weapon aim-point of the marksman. It is not necessary for the targetarea projector 16 to be located adjacent the laser footprint detector18, however, the respective projection and detection areas on the screen6 should be coincident on the screen. There may be some circumstanceswhere these areas do not align for one reason or another, an examplebeing where a portion of the screen needs to be assessed as to whether alaser actually missed the target area.

Image Resolution

There are a number of ways that a marksmanship simulation arrangementcan be achieved using the above elements, but one arrangement is to usea marksmanship training weapon 1 for projecting a non-visible laserfootprint onto the screen 6 and a background projector 4 dedicated toprojecting the background image and which invariably overlays the targetarea. The target area projector 16 for projecting target image 19 intarget area 8 is superimposed over that portion of the background image9 which has been generated by the background projector 4. Other featuresand advantages can be provided by using one or more other elements suchas controlling the movement of the target area within the projectedbackground image while co-coordinating the detection of the target areawith the laser footprint detector.

The resolving power of the human eye is approximately one to two minutesof arc, and can vary between individuals around that average value.Therefore each pixel in the target area image subtends no more than 1minute of arc in order for this image to be at eye-limited resolutionfrom the marksman's viewpoint. This can be achieved by positioning thetarget area projector 16 relatively close to the screen in comparison tothe background projector. Alternatively, the target area projector 16may be positioned further from the screen, but with an optical device 20that focuses the whole image onto a smaller area; these arrangements aredepicted in FIG. 2. The latter solution may be preferred when shootingat targets simulated to be at very long ranges (e.g., 1000 m). Thesesolutions result in the size of the pixels making up the target image tobe small enough so as to not be resolvable by a marksman with normalvision when looking through the sight 2.

A further aspect of the invention is the sole use of a detection of thelaser footprint on a target image within a target area by a detector 18.In one detection arrangement, the laser footprint is smaller than thedetector pixels and the detector outputs a signal representative of thelocation of the detected non-visible laser footprint relative to thepixels of the detector. The footprint location can then be used todetermine the accuracy of the marksman for a single shot as well as fordetermining the extreme spread and other performance measures frommultiple shots.

Various other detection arrangements are also possible, including wherethe detector pixels are larger than the laser footprint, but detectiontechniques can still resolve the location of the footprint to anaccuracy which allows for single and multiple shot determinations of themarksman's accuracy within the pre-determined accuracy as describedearlier.

Details of the arrangement of specific embodiments of the projector/sand detector will be described in greater detail later in thespecification.

Illustrative of the inaccuracy of prior art, FIG. 3 illustrates theprior art projection of the background image including the target imageto illustrate the limitations in target imagery.

A projector 4 generates a background image including a target image 9 onthe screen 6. The target image can be projected anywhere on the screen 6by the projector 4. The target image 9 covers only a few projectorpixels in the target area 8.

Referring to FIG. 4 a the upper image is illustrative of the pixeldensity of target imagery in the prior art and in the case of FIG. 4 bthe upper image is illustrative of a representative and comparativeembodiment of the invention having a much higher pixel image densitythan depicted in FIG. 4 a. The lower images in FIGS. 4 a and 4 b areillustrative of the view of the target image by the marksman eitherunassisted or assisted by the use of a weapon sight. The lower image inFIG. 4 a is a picture of an actual digitally projected image of a targetfrom a prior art simulator and clearly contains visible unwantedartifacts introduced by the pixilated view of the low resolutionprojected target image of the prior art. No such artifacts are visiblein the better than eye-limited resolution target image projected by thetarget projector in the representative embodiment of the invention.

The geometric calculation provided in FIG. 5 is based on the formula forcalculating for the maximum projected pixel size to achieve eye-limitedresolution;

Φ=2a tan [d/(2D)]

θ=mΦ=2a tan [d/(2D)]

Where m=magnification of the sightD=distance between marksman's eye and the screend=maximum distance between the centre of adjacent pixelsθ=angle subtended by a pixel as viewed by the marksman and is set to be1 minute of arc (0.291 milliradians) such that the pixels are ateye-limited resolution

Hence, the maximum size of a pixel (d) for producing a target ateye-limited resolution for a given distance from the screen D is:

$\begin{matrix}{d = {2D\; {\tan \left\lbrack {\theta/\left( {2\mspace{14mu} m} \right)} \right\rbrack}}} \\{= {D\; \theta \text{/}m\mspace{14mu} {for}\mspace{14mu} {small}\mspace{14mu} {values}\mspace{14mu} {of}\mspace{14mu} {\theta.}}} \\{= {D \times 2.91 \times {10^{- 4}/{m.}}}}\end{matrix}$

Using the above equation for one embodiment of the invention in whichD=10 metres yields d=2.91 mm/m. In one embodiment of the invention,magnification m may range from 1 to 10. The target area projector (SonyCX70 Ultra Portable LCD Data Projector, AV Central, Adelaide, SouthAustralia), has a native resolution of 1024×768. Hence, the maximum areathat can be projected by the target area projector such that the targetimage is at eye-limited resolution ranges from 2980 mm×2235 mm (m=1) to298 mm×224 mm (m=10). In this embodiment of the invention, typicaltarget images are tens of mm across and hence the invention readilyachieves eye-limited resolution target imagery. The target areaprojector is placed approximately 1 metre from the screen and achieves afield of view approximately 0.75 metres×0.6 metres. Hence d isapproximately 0.7 mm which yields an eye-limited resolution target imageup to a magnification of ×4 for a marksman positioned 10 metres from thescreen. Eye-limited resolution target images at greater magnificationsmay be achieved in an alternative embodiment of the invention wherein anoptical device focuses the whole image onto a smaller area; as depictedin FIG. 2.

FIGS. 6 a and 6 b depict a graphical illustration of the light intensityfalling along a straight line cross section on the screen in thevicinity of the target image. The maximum contrast ratio that theprojection and screen system is capable of producing can be determinedby projecting a test image where the light intensities rise and fallthrough the minimum and maximum intensities across several pixels forthe background and target projectors producing a checker board effect onthe screen. FIG. 6 a left shows the case where only the target projectoris projecting this test image onto the screen. FIG. 6 a right, shows thecase where only the background projector 4 is projecting the test imageover the entire screen, and the graph shown in the figure is showing theintensity plot in the region of the target image. For the purpose ofthis description it is assumed that the target area projector has beendimmed such that the maximum intensity of light falling on the screen isvery nearly equal to the light intensity of the background projector.Since the light output of the target area projector is focused into asmall area on the screen, the light intensity in the target area will bereduced to match the light levels of the background image where thelight output of the background projector is spread over the entirescreen. To achieve such balancing between projectors of roughly similarlight output capabilities, the target area projector light settings areset low enough to match the light intensity of the background image. Ifthe target area projector does not have sufficient range to achievethis, then a neutral density filter can be placed in front of the targetarea projector lens to further reduce the light output of the targetarea projector.

The maximum light intensity of the target image (6 a left) is denoted byI_(maxt) and the minimum light level by I_(mint). In a similar way, themaximum light intensity of the background image (6 a right) is denotedby I_(maxb) and the minimum intensity of the background image is givenby I_(minb). The contrast ratio of the target image (with only thetarget area projector, 6 a left) is given by I_(maxt)/I_(mint); and thecontrast ratio of the background image is given by I_(maxb)/I_(minb).

FIG. 6 b depicts the effect of superimposing images from the backgroundprojector and the target area projectors in the area of the targetimage, where on the left of FIG. 6 b both projectors are modulatedthrough their full range of intensities across several pixels. FIG. 6 bon the right shows the case where the target area projector is producinglight intensities through its full range, whereas the backgroundprojector is emitting minimal light intensity.

With reference to FIG. 6 b left, if the maximum and minimum intensitiesacross a distance encompassing several background projector pixels aretaken, the background contrast ratio, R_(b) is given by:

R _(b)=(I _(maxt) +I _(maxb))/(I _(mint) +I _(minb))

However the target contrast ratio can be determined by taking the ratioof maximum and minimum intensities over a smaller distance, encompassinga distance that contains only several pixels of the target project. Withreference to FIG. 6 b left, in the regions of 25 mm, 35 mm, 45 mm (wherethe maximum light intensities of the background projector occur), thecontrast ratio is given by:

R _(tmax)=(I _(maxt) +I _(maxb))/(I _(mint) +I _(maxb))

With reference to FIG. 6 b right, where background projector 4 isproducing minimal light intensity, while the target image projector isproducing its maximum contrast the contrast ratio is given by:

R _(tmin)=(I _(maxt) +I _(minb))/(I _(mint) +I _(minb))

For the purposes of illustrating the concepts of contrast ratio andwithout loss of generality, if the two projectors were of matchedbrightness and contrast specifications and the intensities of the targetand background images on the screen were matched by use of a suitablelight filter placed in front of the target area projector, then I_(maxt)and I_(maxb) can be replaced by I_(max) (I_(max) being the maximumscreen intensity that can be produced by each projector). SimilarlyI_(mint) and I_(minb) can be replaced by I_(min) (I_(min) being theminimum screen intensity that can be produced by each projector). Thecontrast ratio equations then become:

R _(b)=(I _(max) +I _(max))/(I _(min) +I _(min))=(2I _(max))/(2I_(min))=I _(max) /I _(min)

That is the contrast ratio over several background pixels is for theintents and purposes of this disclosure, approximately equal to thecontrast ratio of each individual projector pixel.

However, the contrast ratios across a few target image pixels are givenby the following equations. In the region where the background imageprojector is producing a maximum intensity the contrast ratio is:

$\begin{matrix}{R_{tmax} = {\left( {I_{\max} + I_{\max}} \right)/\left( {I_{\min} + I_{\max}} \right)}} \\{= {2{I_{\max}/\left( {I_{\min} + I_{\max}} \right)}}} \\{= {2/\left( {{I_{\min}/I_{\max}} + 1} \right)}} \\{= {2/\left( {{1/R} + 1} \right)}}\end{matrix}$

In the region where the background image projector is producing aminimum intensity the contrast ratio is:

$\begin{matrix}{R_{tmin} = {\left( {I_{\max} + I_{\min}} \right)/\left( {I_{\min} + I_{\min}} \right)}} \\\left. {= {{\left( {I_{\max} + I_{\min}} \right)/2}I_{\min}}} \right) \\{= {{1/2}\left( {{I_{\max}/I_{\min}} + 1} \right)}} \\{= {{1/2}\left( {R + 1} \right)}}\end{matrix}$

Typical contrast ratios of projection systems in a darkened room can beof the order of 500:1 or greater. For the purposes of illustrationconsider the case of using background and target area projectors thatboth have contrast ratios R of 500. The contrast ratio performanceacross the region of several background projector pixels is given byR_(b) and is thus 500. That is the use of two projectors does notadversely affect the contrast achievable over several background pixelsor greater.

However, taking the illustration further, the target image contrastratio in the region of maximum background intensity is given by:

R _(tmaxb)=2/(1/R+1)=2/(1/500+1)≈2 (since 1/500 is much smaller than 1)

That is an R_(tmax) of two implies that the high resolution detail fromthe target image is washed out by the low-resolution of the backgroundprojector if the light intensity of the background projector is high inthe target image area. The contrast ratio in the region where thebackground projector is generating minimum intensity is given by:

R _(tminb)=½(R+1)=½(500+1)=½R≈250

Hence by using two projectors although a higher spatial resolution canbe achieved in the target image, the contrast ratio is, in the best casehalved, and the requirement to achieve this performance is that thebackground projector must produce minimal intensity and contrast in theregion of the target area.

Hence in selecting projectors the simulation engineer should select abackground projector that has specifications for producing regions ofblack that emit the lowest level of light possible. However because thetarget projector has its light output concentrated into a small regionof the screen, the maximum brightness specification of the targetprojector is less critical, but because of the contrast ratio of thetarget image is diminished by the light leaking when the backgroundprojector is emitting “black” the target-projector would benefit byhaving a better contrast specification than the background projector.

In another embodiment of the invention which does not include a screenor background projector, a marksmanship simulator for the training of amarksman having a marksmanship training weapon for projecting anon-visible radiation footprint can include, a target area image capableor reflecting non-visible radiation. In one specific example this couldbe a printed photographic image of a target (an inanimate target) whichis located a distance from the marksman. In one arrangement the targetcould be at a similar distance to the target image used in otherembodiments.

In this arrangement the detector for detecting the reflected footprinton the target includes a density of detector pixels for receiving thenon-visible footprint, and the intensity and size of the non-visibleradiation footprint is such that there is a predetermined accuracy ofthe detection of the location of the footprint.

In the above embodiment the marksmanship simulator includes a means ofilluminating the target. Illumination could be non-visible light fornight marksmanship training usable in conjunction with night visionsystems by the marksman. Further radiation in the visible range can beused to increase the visible intensity of the target during simulateddaytime marksmanship training.

Hit Detection

Modern small arms simulators rely on a single hit-detection camera 20 todetect the laser footprint 7 anywhere over a wide area of the screen 6as depicted in FIG. 7. In some cases, where systems allow multiplefirers, several cameras may be employed for the same purpose (e.g.,multiple cameras for multi-lane systems). The position of the laserfootprint is then correlated to the position of the target. Thehit-detection system sees the screen as a set of distinct blocks, aspictorially represented in FIG. 7, each block typically referred to as apixel 14. In this instance, each pixel represents the projection of thecamera sensory elements onto the screen (as distinct from the pixels ofthe projected imagery).

Typically a computer associated with the hit-detection sensor forms thehit-detection system, and uses the detected intensity and coordinateposition of the detection pixels illuminated by the laser footprint (7in FIG. 7) to calculate the laser footprint position and hence theweapon aim-point. The accuracy of this calculation is dependent on threefactors; the size of the detector pixels for receiving the non-visiblefootprint and the intensity and size of the laser footprint. This isillustrated in FIGS. 8 a, 8 b, 8 c, 9 a, 9 b and 9 c which demonstratedifferent examples in which these three factors are varied.

FIG. 8 a shows the case where the size of the laser footprint is largerthan that of each detector pixel. In this case, the hit-detection systemwill calculate the laser footprint position by determining the footprintcentroid which is the intensity weighted average of the coordinatepositions of each pixel, where the intensity at each detector pixelincludes contributions from the laser footprint and from noise (internalto the camera as well as background thermal noise). Consequently, theaccuracy of this calculation is determined by the signal to noise ratioin the detection process which is predominantly affected by theintensity of the laser footprint. FIG. 8 b shows the case where thesignal to noise ratio is low and consequently the centroid calculationis biased by noise and is inaccurate. When calculating the centroid, athreshold can be applied to reduce the effect of noise. However, in thiscase, the application of a threshold is not sufficient to completelyeliminate the effect of noise because the intensity at each detectionpixel illuminated by the laser footprint has a significant contributionfrom random noise as well as from the laser footprint. FIG. 8 c showsthe case where the signal to noise ratio is high and consequently thecentroid calculation is not biased by noise; application of a thresholdcan substantially eliminate the effect of noise and results in moreaccurate determination of the centroid of the laser footprint. FIG. 9 ashows the case where the size of the laser footprint is smaller thanthat of each detector pixel and in most instances, the laser footprintilluminates a single pixel. In this instance, the hit-detection systemcalculates the laser footprint position to be that of the singleilluminated pixel and the accuracy of the calculation is determined bythe size of the detector pixel. As shown in FIGS. 9 b and 9 c, theeffect of noise is less significant because the illuminated pixel can beuniquely determined after application of a suitable threshold.

In a modern small arms simulator, the hit-detection is performed by astandard charge-coupled device (CCD) camera; the CCD cameras employedtypically have a resolution of 760 pixels (horizontal) by 580 pixels(vertical). For a system allowing a quartet of firers, the screendimension is such that the pixel (as seen by the camera) is a square onthe screen of approximately 4 mm on each side. The size of the laserfootprint in modern small arms simulators is considerably larger thanthis, around 10 mm in diameter. This corresponds to the case shown inFIG. 8 a above and consequently, the size of the pixels does not limitthe accuracy of the hit-detection calculation. The determining factor isnow the signal-to-noise ratio.

To overcome the problem of poor signal-to-noise ratios thatcharacterizes the prior art, the following solutions are proposed: (1) ahit-detection camera that is positioned so as to capture the area of thescreen immediately surrounding the target (in order to increase theamount of signal captured relative to the areas not covered by thesignal which simply add noise to the centroid calculation), (2)hit-detection cameras that have noise floors superior to those used inthe prior art and (3) an eye-safe laser that has a higher intensity andsmaller footprint than those used in the prior art. One embodiment ofthe current invention utilizes all three of these solutions to achievesuperior signal-to-noise ratios and hence highly accurate weaponaim-point calculation.

In addition to adequate signal-to-noise ratio, it is important that theweapon aim-point calculation is not adversely affected by the large sizeof the detector pixel (both in absolute terms and relative to the laserfootprint). The size of each detector pixel is determined by thedimension of the screen captured by the CCD camera relative to thecamera resolution. Consequently, the pixel size can be reduced byincreasing the resolution of the camera or capturing a smaller area ofthe screen. In one embodiment of the current invention, thehit-detection camera only captures a small area of the screen in orderto maximize the signal-to-noise ratio. In this case, the pixel size issmall and the effect is negligible, regardless of the size of the laserfootprint. This is illustrated in FIG. 10 which shows the preferredarrangement of the use of one hit detection sensor (camera) directed tothe target area (the finer grid area central to the upper rightillustration in FIG. 10). These aspects of the invention are furtherillustrated in FIGS. 11 a, 11 b, 12 a and 12 b. FIG. 11 a shows the casewhere the size of the laser footprint is larger than that of eachdetector pixel; FIG. 11 b shows the calculation of the position of thelaser footprint. FIG. 12 a shows the case where the size of the laserfootprint is larger than that of each detector pixel; FIG. 12 b showsthe calculation of the position of the laser footprint.

It should be apparent from the preceding discussion to one skilled inthe art that there is no simple equation which determines the accuracyof a particular embodiment of the hit-detection system as illustrated inFIG. 10. The accuracy is determined by the detector pixel size, the sizeand intensity of the laser footprint and the signal-to-noisecharacteristics of the detector. There is a range of values for theseparameters that satisfies the weapon aim-point accuracy requirementwhich was described earlier in the specification and simulation andexperimentation are required to precisely determine the accuracy of agiven embodiment of the invention. However, appropriate choice for theseparameters allows the design of an embodiment of the invention that hasa pre-determined accuracy that satisfies the weapon aim-point accuracyrequirement which was described earlier in the specification.

In one embodiment the camera (Photron PCI 512 Fastcam, Blink TechnologyAustralia, Pty Limited) with a resolution of 512×512 pixels is placedapproximately 2 m from the screen and captures an area approximately0.25×0.25 m. This results in a pixel size of approximately 0.5 mm.

With regards to the firing weapon the radiation emitted is preferablynon-visible, and can be infra-red or preferably laser, since the smallerlaser footprint provides for increased accuracy, in this embodiment thelaser is an eye-safe infra-red laser (LDM-5-850-0.78, from LaserexTechnologies). In one form, the laser is attached to a suitable weaponand is fired at the screen from a distance of 10 m.

An infrared light filter (Andover 830FG07-165S, Lastek Pty Ltd) isattached to the camera such that only radiation from the laser footprintis detected by the camera.

The laser footprint provided by the laser (LDM-5-850-0.78) isapproximately 4 mm in diameter. Through the use of simulation methods,it may be shown that the relative sizes of pixel (0.5 mm) and laserfootprint (4 mm) the maximum error in the calculation of the laserfootprint position is approximately 0.1 mm. This is similar to the caseshown in FIG. 8 a but the pixel is considerably smaller than that of theprior art. By geometry, if the screen is 10 m from the firer, and thesimulated target is at 100 m, the corresponding error is 1 mm, whichexceeds the weapon aim-point accuracy requirement which was describedearlier in the specification.

The combination of laser (LDM-5-850-0.78), camera (Photron PCI 512Fastcam) and filter (Andover 830FG07-165S) results in signal-to-noiseratios of around 60 dB which is of such magnitude that random noise willhave minimal impact on the accuracy of the calculation of the laserfootprint location. Experimentation with this embodiment of theinvention has shown that when the laser is fired from 4.5 m (want 10 m),the hit-detection system calculates the location of the laser footprintto an accuracy equivalent to a radial standard deviation of 0.01milliradians.

Control of the shape of the laser output from the marksmanship trainingweapon could include the addition of a focusing lens arrangement on thelaser 3 to focus the near parallel rays of the laser 3 to as small aspot on the screen as possible. In cases where the size of the laserfootprint requires reduction this could be achieved by use of anaperture of suitable size in the barrel 3 to restrict the width of thelaser beam and so produce a controlled spot size on the screen 6.

Referring once again to the embodiment of the invention presented inFIG. 1, data from the laser footprint detector 18 is made available tothe computer 11 for processing. A variety of calculations can beperformed by the processor, including displaying either on a separatemonitor or on the screen 6 as required the strikes achieved by themarksman, group calculations and many other details relating toindividual strikes, timing of strikes, comparison with prior resultsachieved by the particular marksman or other marksmen. The data can bestored for later retrieval as required.

In one embodiment the hit detection process includes the following stepsas illustrated in FIG. 13, which where required, is processed in anappropriately programmed general purpose computer, having a processorchip, memory and various input and output mechanisms for receiving,storing and sending data related to the marksmanship simulatorarrangement and marksmanship detector arrangement. Processes 2 to 13illustrate the case where there is a single hit-detection camera as inthe embodiment of the invention described by FIG. 1. If there is arequirement for a second hit-detection camera (if for example, there isa requirement to capture an image of the entire screen) then theadditional processes 15 to 23 are shown in order to illustrate how theprocessing can be replicated and integrated with that of steps 2 to 13.

The processor can provide records (immediately and after a series ofshots) of the laser strikes in tabular and graphical form (digital forviewing and hard copy), the presentation of which is arranged to besuited to the training and qualification of marksmen using the simulatorarrangement.

Step 0 occurs prior to the simulator being run in real time and in thisstep the entire system is calibrated in order to (1) determine theappropriate scaling factor which scales distances from a referencecoordinate system (such as the screen) to the desired coordinate system(such as the firing range being simulated) (2) correct for keystoningand rotation errors resulting from the field of view of the camera beingoffset and rotated relative to the laser footprint.

Radiation (including the laser footprint as well as the background andtarget images) is reflected from the screen (1), and strikes infraredlight filter (2). Infrared filter (2) blocks out the visible portion ofthe radiation and passes only the infrared component of that radiation,which should now be only that from the laser (3). The detector camera(4) now converts the radiation into a pixel image which is an array ofvalues of infrared light intensity (5). An intensity threshold (6) isapplied to this array of values and sets all values below the thresholdto zero, resulting in an array corresponding to the laser footprintagainst a black background (7). The processor now computes the centroid(8) of the laser footprint by taking the intensity weighted average ofthe (x,y) coordinates of each pixel in array. One method to compute theinset aim-point (9) would be to apply an equation of the form:

$X_{i} = {\sum\limits_{j = 1}^{Mi}{\sum\limits_{k = 1}^{Ni}{x_{k}{I_{jk}/\left( {\sum\limits_{j = 1}^{Ni}{\sum\limits_{k = 1}^{Mi}I_{jk}}} \right)}}}}$$Y_{i} = {\sum\limits_{j = 1}^{Ni}{\sum\limits_{k = 1}^{Mi}{y_{j}{I_{jk}/\left( {\sum\limits_{j = 1}^{Ni}{\sum\limits_{k = 1}^{Mi}I_{jk}}} \right)}}}}$

The processor then scales (11) the centroid coordinates into the scaleof the screen coordinate system (12) and then displaces this value (13)according to the offset giving the centroid location relative to areference coordinate on the screen (14). The coordinates (14) nowbecomes an input into ballistic and fall-of-shot computations.

FIG. 13 also shows optional processes 15-23 which illustrate how theprocessing can be replicated and integrated with that of steps 2 to 13where it is desirable to detect the footprint outside of the target areain order to give a low-resolution indication of the extent to which ashot missed the target area.

FIG. 14 depicts the intensity level of the pixel array in one of theaxes before applying a threshold.

FIG. 15 depicts the same pixel intensities as shown in FIG. 14 after theapplication of the threshold where values below the intensity thresholdare set to zero.

FIG. 16 depicts the geometry of the scaling and corrections applied tothe centroid in the detector coordinate system in order to convert themto screen coordinates.

FIG. 17 depicts the output provided by the processor as feedback tomarksman and instructors. Performance data is displayed as thecalculated fall-of-shot after ballistics calculations have been appliedto the location of the laser footprint. As an example, FIG. 17 displaysthe fall-of-shot and extreme spread value for a marksman shooting 5rounds at a target.

What is claimed:
 1. A marksmanship simulator for the training of amarksman including: a target area projector projecting a density ofpixels on the screen such that an individual pixel is not visible to thevision assisted or vision non-assisted marksman, wherein the pixels forma target image within the target area; a screen for receiving andreflecting projected visible and non-visible radiation; a backgroundprojector for projecting an image on the screen and over a target area,wherein the contrast ratio of the target image formed by both thebackground projector and target area projector is substantially that ofthe target area projector.
 2. A marksmanship simulator according toclaim 1 further including, a marksmanship training weapon for projectinga non-visible laser footprint onto the screen; and a detector fordetecting the reflected non-visible laser footprint on the screenwherein the density of the detector pixels for receiving the non-visiblefootprint and the intensity and size of the laser footprint is such thatthere is a predetermined accuracy of the detection of the location offootprint.
 3. A marksmanship simulator according to claim 2 furtherincluding a processor for receiving the detector signal representing thelocation of the non-visible laser footprint and also knowing thelocation of the projected pixels of the background image and target areaand determining the location of the non-visible laser footprint withrespect to one or more of the pixels of either or both the backgroundimage or the target area.
 4. A marksmanship simulator according to claim2 wherein the detector is arranged to detect the non-visible laser onlyif it lies near or within the target area.
 5. A marksmanship simulatoraccording to claim 1 wherein the background projector maximizes thecontrast ratio in the target area by minimizing the brightness in thetarget area projected by the background projector.
 6. A marksmanshipsimulator according to claim 2 further including a mechanism for movingboth the target area projector and the detector such that the detectoris detecting the non-visible footprint in or about the target area.
 7. Amarksmanship detector arrangement for use in a marksmanship arrangementhaving a screen for receiving and reflecting projected visible andnon-visible radiation, a projector for projecting a density of visiblepixels on the screen substantially within a target area and amarksmanship training weapon for projecting a non-visible laserfootprint onto the screen, including a detector for detecting thereflected non-visible laser footprint on the screen wherein the densityof the detector pixels for receiving the non-visible footprint and theintensity and size of the laser footprint is such that there is apredetermined accuracy of the detection of the location of footprint. 8.A marksmanship simulator for the training of a marksman having amarksmanship training weapon for projecting a non-visible radiationfootprint including a target area image capable or reflectingnon-visible radiation, and a detector for detecting the reflectednon-visible radiation footprint from the target wherein the density ofthe detector pixels for receiving the non-visible footprint and theintensity and size of the laser footprint is such that there is apredetermined accuracy of the detection of the location of footprint. 9.A marksmanship simulator according to claim 8 wherein the target areaimage is illuminated.
 10. A marksmanship simulator according to claim 8wherein the target area image is illuminated by non-visible light.